Gradual acquisition of the developmental capacity to differentiate adult structures by the genital disc of Drosophila melanogaster

Summary Diplo-X flies homozygous for the transform-er-2 ^ts (tra-2 ^ts) mutation develop into females at 16° C, while they develop into males at 29° C (Belote and Baker 1982). By means of this conditional mutation, we have carried out a detailed analysis of the development of the genital disc. Temperature shifts between 16 and 29° C, in both directions, and temperature pulses at 29° C, have been applied during the larval growth of tra-2 ^ts homozygous diplo-X flies, and the external derivatives of the genital disc have been analysed. Genital discs shifted from 16 to 29° C rapidly lose their capacity to differentiate female genital structures, while they become able to differentiate male genital structures whose inventory is more complete the earlier in larval development the temperature shift is carried out; moreover, duplicated male genital structures were observed. In the shift from 29 to 16° C, the genital disc loses its capacity to differentiate male genital structures, while it becomes able to differentiate female genital structures. The inventory of male structures is smaller, and the inventory of the female structures is more complete, the earlier in larval development the temperature is shifted. No duplicated female or male genital structures were observed in the downshift experiment. With respect to the analia, the shift from 16 to 29° C resulted in the quick formation of pure male anal plates, while in the opposite shift the formation of pure female anal plates occurred gradually. Moreover, the time course for the dorsal and ventral anal plates to show normal female phenotype was different: when the dorsal anal plates were completely normal, it was still possible to find incomplete ventral anal plates. In the pulse experiment at 29° C, the genital disc is able to differentiate both female and male genital structures, although the inventory of the latter ones was not complete. In addition, the capacity of the genital disc to differentiate male genital structures depended on the duration of the temperature pulse. The anal plates were always female, although they showed a reduction in their size, the ventral female anal plate being more affected than the dorsal one. No male anal plates were observed. The results have revealed that the genital disc follows a sequence in its capacity to differentiate female or male adult structures. We suggest that this sequence reflects the sequence of determination events occurring in the genital disc during its larval growth. In addition, results shown here provide evidence for the existence in the female genital primordium of a set of cells capable of giving rise either to female genital structures (ventral vaginal plates) or to male genital structures (hypandrium and penis apparatus). We also present evidence supporting the previous idea of two primordia for the anal plates.     

The development of the Drosophila genital disc

The imaginal discs of Drosophila melanogaster, which form the adult epidermal structures, are a good experimental model for studying morphogenesis. The genital disc forms the terminalia, which are the most sexually dimorphic structures of the fly. Both sexes of Drosophila have a single genital disc formed by three primordia. The female genital primordium is derived from 8(th) abdominal segment and is located anteriorly, the anal primordium (10 and 11(th) abdominal segments) is located posteriorly, and the male genital primordium from the 9(th) abdominal segment lies between them. In both sexes, only two of these three primordia develop to form the adult terminalia. The anal primordium develops in both sexes but, depending on the genetic sex, will form either male or female analia. However, only one of the genital primordia develops in each sex, forming either the male or the female genitalia. This depends on the genetic sex of the fly. Therefore, the genital disc is a very good experimental model of how the sex-determination and homeotic genes - which determine cell identity - interact to direct the development of a population of cells into male or female terminalia. It has been proposed that the sexually dimorphic development of the genital disc is the result of an integrated genetic input, made up by the sex-determination gene doublesex and the homeotic gene Abdominal-B. This input acts by modulating the response to Hedgehog, Wingless, and Decapentaplegic morphogenetic signals.     

Juveniles of Kyphosus vaigiensis (Quoy and Gaimard 1825) with reference to a senior synonym of Cantharus lineolatus Valenciennes 1830

The juveniles of Kyphosus vaigiensis (Quoy and Gaimard 1825), collected from the Indian Ocean and Japanese waters, are described with some ontogenetic morphological changes based on six specimens having 14 dorsal and 13 anal fin soft rays, 56–62 scales in a longitudinal row along the midbody, and 30–32 gill-rakers on the first gill-arch. The juveniles of K. vaigiensis smaller than ca. 42 mm in standard length (SL) have the proximal parts of the dorsal and anal fin soft-rayed portions covered with small scales, and the single outer row of the upper jaw teeth consisting of incisor-like and conically pointed teeth, the former with polycuspid tips differing from the specimens greater than ca. 68 mm SL. The holotype of Cantharus lineolatus Valenciennes 1830, 41.5 mm SL, was included here in the juveniles as K. vaigiensis. Therefore, K. vaigiensis is recognized as a senior synonym of C. lineolatus.     

Suppression of abdominal legs inDrosophila melanogaster

Summary Drosophila melanogaster normally have six thoracic legs and no abdominal legs. However, one or two legs often appear in the first abdominal segment ofbithoraxoid mutants. The extent to which these extra legs develop is determined both by thecis-regulatory action ofbithoraxoid lesions onUltrabithorax and by the number of copies of the adjacent homeotic geneabdominal-A. Thebithoraxoid region does notcis-regulateabdominal-A.     

Molecules and the Body Plan: TheHoxGenes of Cirripedes (Crustacea)

Among arthropods, Cirripedia (barnacles) are remarkable in that they completely lack abdominal segments. This feature prompted us to study theHoxgenes of three cirripede species, representing a wide array of the diversity of these organisms, a segmented sessile barnacle,Elminius modestus(Thoracica), the parasite of a crab,Sacculina carcini(Rhizocephala), and the burrowing barnacleTrypetesa lampas(Acrothoracica). Using PCR amplification of genomic DNA and cDNA and library probing, we have found seven clear cirripedian homologues of the eight homeoticHoxgenes known in insects, includinglabialandproboscipediahomologues, that were not previously reported in crustaceans. In addition we have isolated a divergentAntp-like gene, namedDiva, that we homologize to theftzgene of insects. The homeotic geneabdominalA(abdA) was not retrieved from any of these three cirripede species. By contrast, we have found all eight homeotic homologue genes, includingabdA, inUlophysema oeresundense, a crustacean possessing a well-developed abdomen, belonging to the Ascothoracica, generally thought to be the sister group of Cirripedia. Since we have found in barnacles homeobox-containing genes that are more divergent from theAntennapediatype than the typicalabdA, we believe that abona fide abdAgene would not have escaped our search. Hence, theabdAgene has been lost or is profoundly derived in sequence during the evolution leading to the cirripedian lineage. If confirmed, the lack ofabdAwould represent the first case in which the loss of a homeotic gene is correlated with a change in body plan during the evolution of metazoans.     

The evagination of the genital imaginal discs ofDrosophila melanogaster

Summary The morphology of the evaginating female genital disc ofDrosophila melanogaster was examined at different stages of metamorphosis. The observations show that the internal genital organs are derived from the anterior half of the disc and that their morphogenesis is mainly a protrusion of the different primordial areas of the disc epithelium. The external genital and anal derivatives originate from the posterior half of the disc, which undergoes complex rearrangements during metamorphosis. The disc opens along the posterior margin and the dorsal and ventral epithelia evert and thereby completely reverse their anteroposterior orientation. Dramatic elongation has been observed during the formation of the seminal receptacle. The cells of the repressed male genital primordium do not form any recognizable structures and are assumed to be eliminated during metamorphosis.     

花生根瘤菌Bradyrhizobium sp.MM6 Ⅲ型分泌系统的结构和功能

【目的】探究花生根瘤菌Bradyrhizobium sp.MM6的Ⅲ型分泌系统(T3SS)的结构及其在根瘤菌与不同宿主建立共生关系中的作用。【方法】同源比对分析菌株MM6的T3SS基因簇的结构特征,并采用三亲本接合转移的方法构建T3SS调节基因ttsI突变菌株;通过蛭石结瘤和石蜡切片实验,比较突变体与野生型的共生固氮表型差异。【结果】经预测,MM6的T3SS基因簇编码区长约34.1 kb,可分为3个区域,包含10个保守结构基因和8个效应蛋白基因,与B.diazoefficiens USDA110相应基因的序列相似性为83%–93%;成功构建了MM6的ttsI突变株;ttsI突变株与野生型分别与花生(S523和Y45)、野大豆和大豆中黄57结瘤,ttsI突变体在花生中的总瘤数显著增加(P<0.05),根瘤中含菌细胞更多;ttsI突变体在野大豆中平均每株植物增加4个根瘤,根瘤中含菌细胞更多,地上部干重相比野生型MM6显著增加(P<0.05);在大豆中黄57中,野生型MM6能形成红色的有效根瘤,ttsI突变体不结瘤,且植株叶片发黄,地上部干重相比野生型MM6显著降低(P<0.05)。【结论】MM6的T3SS在花生和野大豆共生体系中起着有害的作用,而在大豆中黄57的共生体系中起着有利的作用。     

The 5S DNA units of bread wheat (Triticum aestivum)

A collection of 44 cloned 5S DNA units fromTriticum aestivum cv. Chinese Spring were grouped into 12 sequence-types based on sequence similarity and the respective consensus sequences were then produced. The relationship between these 12 consensus sequences (T. aestivum S 1-S 8 andT. aestivum L 1-L 4), together with two clones sequenced byGerlach andDyer, and the 5S DNA consensus sequences from diploidTriticum spp. were then determined by numerical methods. Both phenetic and cladistic analyses were carried out. The following wheat 5S DNA sequences were found to group with respective sequences from diploidTriticum spp.:T. aestivum S 4, S 6 withT. tauschii S;T. aestivum S 3 withT. monococcum S andT. monococcum S-Rus 7;T. aestivum L 1 andT. aestivum L-G&D withT. speltoides L;T. aestivum L 2, L 3 withT. tauschii L;T. aestivum L 4 withT. monococcum L andT. monococcum L-Rus 12. The analyses suggested that 5 out of the 65S Dna loci present in wheat were identified at the sequence level. The locus that could not be identified in this analysis was the5S Dna-B 1 locus. A group ofT. aestivum sequences (T. aestivum S 1, S 7, S 8, S-G&D) were found to be distinct from the other 5S DNA sequences in the data base. The existence of the distinct group of 5S DNA sequences suggests that there is a gap in our current understanding of wheat evolution with respect to the5S Dna loci.     

Embryonic origin of the imaginal discs of the head of Drosophila melanogaster

The embryonic development of the primordia of the Drosophila head was studied by using an enhancer trap line expressed in these structures from embryonic stage 13 onward. Particular attention was given to the question of how the adult head primordia relate to the larval head segments. The clypeo-labral bud to the stage 13 embryo is located at a lateral position in the labrum adjacent to the labral sensory complex (epiphysis). Both clypeo-labral bud and sensory complex are located anterior to the engrailed-expression domain of the labrum. Throughout late embryogenesis and the larval period, the clypeo-labral bud forms integral part of the epithelium lining the roof of the atrium. The labial disc originates from the lateral labial segment adjacent to the labial sensory complex (hypophysis). It partially overlaps with the labial en-domain. After head involution, the labial disc forms a small pocket in the ventro-lateral wall of the atrium. The eye-antenna disc develops from a relatively large territory occupying the dorso-posterior part of the procephalic lobe, as well as parts of the dorsal gnathal segments. Cells in this territory are greatly reduced in number by cell death during stages 12–14. After head involution, the presumptive eye-antenna disc occupies a position in the lateral-posterior part of the dorsal pouch. Evagination of this tissue occurs during the first hours after hatching. In the embryo, no en-expression is present in the presumptive eye-antenna disc. en-expression starts in three separate regions in the third instar larva.     

Transdetermination in the homeotic eye--antenna imaginal disc of Drosophila melanogaster

The effects of homeotic mutations on transdetermination in eye-antenna imaginal discs of Drosophila melanogaster were studied. After 12 days of culture in vivo, antenna discs transformed to ventral mesothorax by AntpNs or AntpZ, transdetermined to notum and wing structures four to five times more frequently than the corresponding wild-type antenna discs. Likewise, eye discs transformed to dorsal mesothorax by eyopt transdetermined to leg structures, also extremely frequently (90%). It seems that, during culture, homeotic antenna as well as homeotic eye discs tend to complete the structural inventory of the mesothoracic segment. Transdetermination in the homeotic disc parts is interpreted as a regeneration process which reestablishes an entire segment, i.e., the ventral mesothoracic portion (leg) in the antenna disc regenerates dorsal mesothoracic parts, and the dorsal mesothoracic portion in the eye disc (wing) regenerates ventral mesothoracic parts, respectively. This implies that antenna and leg discs (ventral qualities) as well as eye and wing discs (dorsal qualities) are serially homologous. The transdetermination frequency of the untransformed eye disc to notum and wing structures is enhanced by Antp to the same extent as is the transdetermination frequency of the antenna disc. The first allotypic wing disc structure formed by the eye disc is notum, followed by structures of the anterior wing compartment and finally by posterior wing structures. No evidence for such a sequence was found in the transdetermination pattern of the antenna disc.     

<Emphasis Type="Italic">Doederleinia gracilispinis</Emphasis> (Fowler, 1943), a junior synonym of <Emphasis Type="Italic">Doederleinia berycoides</Emphasis> (Hilgendorf, 1879), with review of the genus

A poorly known acropomatid, Rhomboserranus gracilispinis Fowler, 1943, was originally described on the basis of specimens from the Philippines. Since the recognition of Rhomboserranus as a junior synonym of Doederleinia, R. gracilispinis had been considered a valid species of Doederleinia. Examination of the holotype of R. gracilispinis and other type series of nominal species of Doederleinia showed them to be included in the single species D. berycoides (Hilgendorf, 1879). The sole representative of Doederleinia is distributed from Japan to northwestern Australia. This species is distinguishable from other acropomatids by the following combination of characters: head and body red; nine dorsal-fin spines; three anal-fin spines; no luminous organ; a row of conical teeth with a large canine tooth medially on lower jaw; large conical teeth on anterior part of outer margin with two or three large canine teeth on inner margin on upper jaw; and anus situated just anterior to origin of anal fin.     

Cell lineage restrictions in the genital disc ofDrosophila revealed byMinute gynandromorphs

Summary The genital imaginal disc ofDrosophila differentiates the terminalia, i.e. the genitalia and analia, of both sexes. It represents a composite anlage, containing a female genital primordium, a male genital primordium and an anal primordium. In normal males and females, only one of the two genital primordia differentiates; the other is developmentally repressed. Therefore, cell-lineage relationships between the male and female genital primordia can only be studied in sexual mosaics which differentiate female and male cells. We producedMinute (M)non-Minute(M⁺) gynandromorphs and selected those with sexually mosaic terminalia for a cell-lineage analysis. In these mosaics, either the male (XO) or female (XX) cells wereM ⁺ and thus had a growth advantage. The differential growth rates served as a tool to detect clonal restrictions. In control gynandromorphs (M ⁺M ⁺), the amount of female genitalia differentiated was largely independent of the amount of male genitalia present. In contrast, male and female anal structures, as a rule, added up to one full set. The same was true for the experimentalMM ⁺ gynandromorphs, but the contribution ofXX andXO cells to mosaic terminalia changed drastically due toM ⁺ cells competing successfully against the more slowly growingM cells. Specific subsamples ofMM ⁺ gynandromorphs showed thatM cells in a non-mosaic primordium are shielded from cell competition taking place in the neighbouring mosaic primordium. We conclude that the three primordia of the genital disc represent developmental compartments. In the genital primordia, even developmentally repressedM ⁺ cells compete successfully against developmentally activeM cells.     

Sequences variation and classification of B-hordein genes in hull-less barley from the Qinghai-Tibet Plateau

The goal of this study is to understand the evolution relationship of the members of the B-hordein gene family in hull-less barley by analysis of their structure and to explore their utility in grain quality improvement. Six copies of the B-hordein gene (Hn1-Hn3, Hn7-Hn9) were cloned from six hull-less barley cultivars collected from Qinghai-Tibet Plateau and molecularly characterized. Comparison of their predicted polypeptide sequences with the published data suggested that they all share the same basic protein structures. In addition, we found that the C-terminal end sequences of all B-hordeins shared a similar feature. In the six clones and the other three published genes (Hn4, Hn5, and Hn6) from hull-less barley, Hn2 and Hn7 contained the identical C-terminal end sequence DIMPVDFWH. Hn3, Hn4, Hn5, Hn8 and Hn9 also shared the common sequence DIMPPDFWH, which was similar to that of a B-hordein reported previously. Both Hn1 and Hn6 exhibited differences in their C-terminal end sequences, and they clustered into different subgroups. The B-hordeins with identical C-terminal end sequences were clustered into the same subgroup, so we believe that B-hordein gene subfamilies possibly can be classified on the basis of the conserved C-terminal end sequences of predicted polypeptide. Phylogenetic analysis also indicated that there is a relatively weak identity between our predicted B-hordeins and those reported from H. chilense and H. brevisubulatum. All of our nine predicted B-hordeins were clustered together and other B-hordeins formed another cluster. The possible use of these genes in relation to barley quality is discussed. Published in Russian in Molekulyarnaya Biologiya, 2008, Vol. 42, No. 1, pp. 63–70. The text was submitted by the authors in English     

Effects of Polycomb Group Mutations on the Expression of Ultrabithorax in the Drosophila Visceral Mesoderm

The Polycomb group (PcG) genes encode repressors of many developmental regulatory genes including homeotic genes and are known to act by modifying chromatin structure through complex formation. We describe how Ultrabithorax (Ubx) expression is affected by the PcG mutants in the visceral mesoderm. Mutant embryos of the genes extra sex combs (esc), Polycomb (Pc), additional sex combs (Asx) and pleiohomeotic (pho) were examined. In each mutation, Ubx was ectopically expressed outside of their normal domains along the anterior-posterior axis in the visceral mesoderm, which is consistent with the effect of PcG proteins repressing the homeotic genes in other tissues. All of these four PcG mutations exhibit complete or partial lack of midgut constriction. However, two thirds of esc mutant embryos did not show Ubx expression in parasegment 7 (PS7). Even in the embryos showing ectopic Ubx expression, the level of Ubx expression in the PcG mutations was weaker than that in normal embryos. We suggest that in PcG mutations the ectopic Ubx expression is caused by lack of PcG repressor proteins, while the weaker or lack of Ubx expression is due to the repression of Ubx by Abd-B protein which is ectopically expressed in PcG mutations as well.     

Genetic complementation of a floral homeotic mutation,apetala3, with an Arabidopsis thaliana gene homologous to DEFICIENS of Antirrhinum majus

Among the homeotic mutants with altered floral organs, two mutants of Arabidopsis thaliana, apetala3 and pistillata, and two mutants of Antirrhinum majus, deficiens and globosa, have a homeotic conversion of the floral organs in whorl 2 and 3, namely petals to sepals and stamens to carpels. We have isolated a homologue of the DEFICIENS gene from A. thaliana wild type and shown complete complementation of apetala3 mutation by introducing the isolated gene using Agrobacterium-mediated transformation. These results show that the APETALA3 is a homologue of DEFICIENS structurally and functionally. The 5-upstream region of APETALA3 contains three SRE-like sequence, where MADS box-containing proteins are assumed to bind and regulate expression in tissue-and stage-specific manner.     

Terminal versus segmental development in the Drosophila embryo: the role of the homeotic gene fork head

Summary Mutations of the homeotic gene fork head (fkh) of Drosophila transform the non-segmented terminal regions of the embryonic ectoderm into segmental derivatives: Pre-oral head structures and the foregut are replaced by post-oral head structures which are occasionally associated with thoracic structures. Posterior tail structures including the hindgut and the Malpighian tubules are replaced by post-oral head structures associated with anterior tail structures. The fkh gene shows no maternal effect and is required only during embryogenesis. The phenotypes of double mutants indicate that fkh acts independently of other homeotic genes (ANT-C, BX-C, spalt) and caudal. In addition, the fkh domains are not expanded in Polycomb (Pc) group mutant embryos. Ectopic expression of the homeotic selector genes of the ANT-C and BX-C in Pc group mutant embryos causes segmental transformations in terminal regions of the embryo only in the absence of fkh gene activity. Thus, fkh is a region-specific homeotic rather than a selector gene, which promotes terminal as opposed to segmental development. Offprint requests to: Institut für Biologie II (Genetik), Universität Tübingen, Auf der Morgenstelle 28, D-7400 Tübingen, Federal Republic of Germany     

Isolation and identification of Triticum aestivum L. em. Thell. cv Chinese Spring-T. peregrinum Hackel disomic chromosome addition lines

Analyses of RFLPs, isozymes, morphological markers and chromosome pairing were used to isolate 12 Triticum aestivum cv Chinese Spring (genomes A, B, and D)-T. peregrinum (genomes S^v and U^v) disomic chromosome addition lines. The evidence obtained indicates that each of the 12 lines contains an intact pair of T. peregrinum chromosomes. One monosomic addition line, believed to contain an intact 6S^v chromosome, was also isolated. A CS-7U^v chromosome addition line was not obtained. Syntenic relationships in common with the standard Triticeae arrangement were found for five of the seven S^v genome chromosomes. The exceptions were 4S^v and 7S^v. A reciprocal translocation exists between 4S¹ and 7S¹ in T. longissimum and evidence was obtained that the same translocation exists in T. peregrinum. In contrast, evidence for syntenic relationships in common with the standard Triticeae arrangements were found for only one U^v chromosome of T. peregrinum.; namely, chromosome 2U^v. All other U^v genome chromosomes are involved in at least one translocation, and the same translocations were found in the U genome of T. umbellulatum. Evidence was also obtained indicating that the centromeric regions of 4U and 4U^v are homoeologous to the centromeric regions of Triticeae homoeologous group-6 chromosomes, that the centromeric regions of 6U and 6U^v are homoeologous to the centromeric regions of group-4 chromosomes, and that 4U and 4U^v are more closely related overall to Triticeae homoeologous group-6 chromosomes than they are to group-4 chromosomes.     

Negative regulation ofUltrabithorax expression byengrailed is required for proper specification of wing development inDrosophila melanogaster

In both vertebrates and invertebrates, homeotic selector genes confer morphological differences along the antero-posterior axis. However, insect wing development is independent of all homeotic gene functions, reflecting the ground plan of an ancestral pterygote, which bore wings on all segments. Dipteran insects such asDrosophila are characterized by a pair of wings in the mesothoracic segment. In all other segments, wing development is essentially repressed by different homeotic genes, although in the metathorax they are modified into a pair of halteres. This necessitates that during development all homeotic genes are to be maintained in a repressed state in wing imaginal discs. In this report we show that (i) the function of the segment polarity geneengrailed (en) is critical to keep the homeotic selector geneUltrabithorax (Ubx) repressed in wing imaginal discs, (ii) normal levels of En in the posterior compartment of haltere discs, however, are not enough to completely repressUbx, and (iii) the repression ofUbx byen is independent of Hedgehog signalling through which the long-range signalling ofen is mediated during wing development. Finally we provide evidence for a possible mechanism by whichen repressesUbx. On the basis of these results we propose thaten has acquired two independent functions during the evolution of dorsal appendages. In addition to its well-known function of conferring posterior fate and inducing long-range signalling to pattern the developing appendages, it maintains wing fate by keepingUbx repressed.     

Cloning and sequencing of nifBHDKENX genes of Paenibacillus massiliensis T7 and its nif promoter analysis

A 324 bp of nifH fragment was PCR amplified from Paenibacillus massiliensis T7 using the universal degenerate primers. The PCR-amplified nifH fragment was labeled with DIG and then used as a probe in Southern blot analysis. Southern blot result showed that there were two positive signals, indicating that there might be two copies of nifH in P. massiliensis T7. A total of 10254 bp DNA sequence containing purD and nifBHDKENX was obtained by five rounds of inverse-PCR amplification. The predicted proteins of nifBHDKENX had high homology with those from other nitrogen-fixing bacteria. Only one putative σ⁵⁴-dependent promoter sequence was detected upstream of the nifB gene and nifBHDKENX were likely to be organized in one operon. Assays of β-galactosidase activity of P. massiliensis T7PB carrying a nifB-lacZ fusion under different concentrations of NH⁺₄ and O₂ showed that the expression of nifB-lacZ was strongly inhibited by O₂.